Electrofluid-dynamic generator



Nov. 4, 1969 M. o. L AwsoN 3,476,959

ELECTROFLUIDFDYNAMIC GENERATOR Filed July 6, 196'? 4 Sheets-Sheet 2INVENTOR,

NOV- 4, 1969 M. o. LAWSON ELECTROFLUID-DYNMIC GENERATOR 4 Sheets-Sheet 3Filed July 6. 1967 /V/VU/e/C B Y WM@ Nov. 4, 1969 M. o. LAWSON 3,476,959

ELEGTROFLUID-DYNAM1C GENERATOR I Filed July 6, 1967 4 Sheets-Sheet 4.

United States Patent O 3,476,959 ELECTROFLUID-DYNAMIC GENERATOR Maurice0. Lawson, Dayton, Ohio, assigner to the United States of America asrepresented by the Secretary of the Air Force Filed July 6, 1967, Ser.No. 651,628 Int. Cl. H02n 4/00 U.S. Cl. 310- 8 Ciaims ABSTRACT OF THEDISCLOSURE In an electrouid-dynamic generator an elongated coronadischarge electrode is positioned adjacent an elongated attractorelectrode with a channel provided between. The ends of the coronadischarge electrode and the attractor electrode are shaped to form anexpansion nozzle adjacent the edge of the corona discharge electrode. Acollector electrode is spaced from the corona discharge and attractorelectrodes in line with the nozzle. A shield electrode is providedbetween the nozzle and the collector electrode. A high pressure, hightemperature gas is directed through the nozzle toward the collectorelectrode. An electric ield is established between the corona dischargeelectrode and attractor electrode. The gas after passing the collectorelectrode is recirculated past the corona discharge and attractorelectrodes to provide a low pressure region adjacent a portion of thecorona discharge electrode shielded from the high pressure gases withinthe nozzle to aid in the establishment of a corona discharge from thecorona discharge electrode. The recirculated gas also aids in keepingthe charge particles in the main stream from reaching insulatorsprovided .between the shield electrode and the collector electrode andalso permits the use of an increased width in the conversion sectionwhich in, turn allows an increased length in the conversion section andtherefore a corresponding higher voltage.

BACKGROUND OF THE INVENTION The electrofluid-dynamic process makes useof nonconducting gas to transport unipolar charges directly against theaction of an electrostatic field. In this process charged particles ofone polarity are transported by fluid-dynamic energy from the groundedentrance electrode to the collector electrode against the electrostaticiield which is generated by the electrical potential of the collectorelectrode.

In the electrofluid-dynamic energy conversion process, the efficiency,the power output of a generator of a given size, depends on the ratio ofthe total charge on the charged particles to the mass of the carrierfluid, in the energy conversion section between the two electrodes, thatis substantially on the space charge density. The limitation on thespace charge density is the dielectric strength of the working fluid andin actual practice the maximum ield strength can be in the neighborhoodof one half the dielectric strength. With the conveyor gas, carrying thespace charge, passing through a cylindrical conversion section as shownin FIG. lA, neglecting end eects, the maximum field strength due tospace charge occurs next to the surface of the section, and isproportional to the space charge in a given length of the sectiondivided by the surface area of the same length. Therefore by increasingthe surface area of the conversion section, the total space charge inthe conversion section can be increased without dielectric breakdown.This can be accomplished by providing a beam which is elongated in onedimension to form a rectangular-shaped beam as shown in FIG. lB. Otherconfigurations can be used ice which will provide an increased surfacearea for a given cross-sectional area of the beam, for example, anannular beam configuration or a radial -beam configuration.

SUMMARY OF THE INVENTION According to this invention, use is made of anelongated beam conguration to provide a larger charge to mass ratio andthus provide a greater eiiiciency. A corona discharge is providedbetween an elongated knife-edge electrode which is shaped and positionedto provide an elongated divergent nozzle adjacent the knife-edgeelectrode. A high temperature, high pressure gaseous material such assteam or mercury vapor is supplied to the divergent nozzle so that aportion of the gaseous material is condensed around the chargedparticles to provide droplets of the order of 1/100 micron diameter orlarger to provide a greater drag interaction force between the chargesand the gaesous ilow such that there is negligible slip between thecharged droplets and the How. A portion of the knife-edge electrode isshielded from the high pressure gas to more readily permit theestablishment of the corona discharge, A secondary ow path is directedinto the conversion channel to restrict the beam ow and to provide agreater volume flow of working medium which results in greaterelectrical power extraction. The shielded portion of the knife-edgeelectrode lies in the secondary flow which is at a lower pressure.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1A is a diagrammatic illustrationshowing the cross section of the gas stream in prior art devices;

FIG. 1B is a diagrammatic illustration showing one possible gas streamcross section according to this invention;

FIG. 2 is a crosssectional view of an electrouiddynamic generatoraccording to one embodiment of the invention;

FIG. 3 is an enlarged cross-sectional View of the nozzle structure forthe device of FIG. 2;

FIG. 4 is a diagrammatic view partially in section of anelectrouid-dynamic structure according to another embodiment of theinvention;

FIG. 5 is an enlarged cross-sectional view of a portion of one of theunits of the device of FIG. 4;

FIG. 6 is a reduced top plan view of one of the collector divergentchannel forming structures of the device of FIG. 5; and

FIG. 7 is an enlarged sectional view of the nozzle structure for thedevice of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION Reference is now made to FIG. 2 ofthe drawing, which shows an electrouid-dynamic energy conversion system10 having an annular knife-edge electrode 11 and an annular attractorelectrode 13 with an annular channel 14 therebetween. As shown in FIG.3, the tip of the knife-edge electrode projects toward the attractorelectrode and forms together therewith a divergent nozzle 15 asindicated by the different length lines L1 and L2. A high temperature,.high pressure gaseous material such as steam or mercury vapor at-between 20 and 400 atmospheres and at a temperature, selected in themanner 'as will be explained later, is supplied to the nozzle 15 throughchannel 14, supply inlet 16 and an annular channel 18. Knifeedgeelectrode 11 is insulated from the attractor electrode 13 by means ofannular insulators 20 and 21. O-n'ngs 22 provide a pressure seal for thegaseous material in channel 18. A plurality of bolts 25, two of whichare shown, secure the knife-edge electrode 11 to the attractor electrode13 and are insulated from the attractor electrode by insulators 27.

Collector electrode structure 29 is positioned downstream of the nozzle15. A shield electrode 30 having an electrical connector 31 ispositioned between the connector electrode structure 29 and the nozzle15. The shield electrode 30 has inner and outer annular members 32 and32 electrically interconected by a plurality of connector members 34,one of which is shown. The shield electrode member 32 is electricallyconnected to the attractor electrode 13 by means of a plurality ofconnectors 34', one of which is shown. The desired electrical potentialis applied to the corona discharge electrode 11 by means of leader 28.The collector electrode structure is supported on the shield structure30 by means of annular insulators 33 and 33'. The anode structure hasannular conical members 35 and 36 which form a passage 37 divergent inthe direction of the ow. An end member 40 is secured to the conicalmember 36 and acts to direct a secondary flow of gaseous materialbetween cylindrical elements 42 and 43 back through passages 45 and 46past the knife-edge electrode 11 and attractor electrode 13. Structures35 and 40 are interconnected by means of a plurality of spacedconnectors 38, one of which is shown. Output electrode 39 is connectedto end member 40. The conical elements 35 and 36 are supported oninsulators 33 and 33 by means of annular support members 49 and 50,respectively. The width of the conversion section is limited by a pairof annular insulators 52 and 53 supported on support members 49 and 50,respectively. Since gaseous material is continually being suppliedthrough the nozzle, an outlet 55 is provided in the housing 56 to bleedoi an amount of gaseous material equal to that supplied through nozzle15. Though not shown, the gaseous material from outlet 55 could bereturned to the gaseous material supply.

Other arrangements for this device may be used, for example, otherannular streams could be positioned radially outward and surrounding thestream shown, Also arrangements could be used wherein attractorelectrodes are positioned on both sides of the corona dischargeelectrode or needle electrodes may be placed on each side of anattractor electrode.

In the operation of the device, a high temperature, high pressure gas issupplied to nozzle through supply inlet 16 and annular channels 18 and14. Thus gas ows from nozzle 15 through passage 37, back betweenelements 42 and 43 to provide a secondary flow through passages 45 and46 adjacent the knife-edge electrode and attractor electrode,respectively. The secondary ow mixes with the main flow from nozzle 15between the nozzle and the conversion section and in the conversionsection between insulators 52 and 53.

The desired potential is established between .the knifeedge electrode 11and the vattractor electrode 13 to establish a corona discharge betweenthe knife-edge electrode and the attractor electrode. Since the portionof the knife-edge electrode 11', shown in FIG. 3, is in the lowerpressure secondary stream, a Corona discharge is readily established inthis region of the knife-edge electrode. EX- cept when a gas such as airis used, the ow of gaseous material in the divergent nozzle 15 causes aportion of the gaseous material to condense around the charged particleswhich are then carried to the collector electrode structure by draginteraction force. Because .the charged particles are carried away bythe high velocity gaseous material, substantially no charge reaches theattractor electrode so that the attractor current is substanitally zero.Any condensed material is returned to the gaseous phase in the expansionpassage 37 so that substantially dry gas ows through passages 45 and 46.The tempera- .ture of the inlet gaseous material is selected to providesubstantially dry gaseous flow in the passages 45 and 46 and will bedetermined by various factors such `as the geometry and materials usedin the apparatus.

A device that is more compact and easier to construct than the devicedescribed is shown in FIG. 4. In this device, the collector electrodestructure 59 is positioned in the center of a cylindrical chamber.Annular nozzle structure 61 surrounds the collector structure anddirects `a gaseous stream radially inwardly .toward the collectorstructure. With this arrangement, a plurality of electroiiuid-dynamicunits can be located within a single cylindrical enclosure 63 with thecollector structure 59 being supported between insulators 65 and 66 withthe collector lead 67 passing out through one of the insulators. Sinceall of the fluid dynamic units are identical, one of these units will bedescribed with respect to FIGS. 5, 6 and 7.

The nozzle structure shown in greater detail in FIG. 7 has an annularknife-edge electrode 70 and an attractor electrode 71 forming an annularpassage 74 and nozzle 75. An inlet 77 feeds an annular channel 78 whichsupplies gaseous material to annular passage 74. Insulating spacers 80and 81 with O-ring seals 82 are provided between the knife-edgeelectrode 70 and attractor electrode 71. The knife-edge electrode issecured to the attractor electrode by means of a plurality of bolts 85,one of which is shown. Bolt is insulated from knife-edge electrode Vbyinsulator 87. Lead 89 is connected to knife-edge electrode for applyingthe desired potential thereto. The attractor electrode may be connectedat ground potential through the gas supply inlet 7'/ as shown or may beconnected to the shield electrode 90, made up of two annular members'90a and b, which are connected at ground potential by means of aplurality of annularly spaced support connectors 93. The gas stream fromthe nozzle is directed toward the centrally positioned individualcollector structures 60 which make up the overall collector structure59. Each of the collector structures 60 has a pair of circular membersand 96 which are shaped to form a divergent passage 98 each having a webcenter support member 99 as shown in FIG. 6. The web support member 99are positioned and supported between collector flow directors 101. Theconversion section passage width is limited by annular insulators 103and 104 secured to annular screen members '90a and 90b and members 95and 96, respectively. A secondary ow path 108 is provided between theunits with secondary flow passages 109 and 110 provided adjacent thenozzle 75. The operation of this device is substantially the same asthat of the device of FIG. 2.

Various materials may be used in these devices for eX- ample the metalparts can be stainless steel and the insulators can be ceramic material.Also though a pressure range of 20 to 400 atmospheres has beendescribed, it is to be understood that higher pressures may be used toadvantage if apparatus is built to withstand the higher pressures.

There is thus provided an electrofluid-dynamic conversion system whichprovides greater efficiency than prior art devices.

While certain specific embodiments have been described in detail, it isobvious that numerous changes may be made without departing from thegeneral principles and scope of the invention.

I claim:

1. An electrouid-dynamic energy conversion system comprising: an elongednozzle; means for supplying a ow of high pressure gaseous materialthrough said nozzle; said nozzle being formed by a knife-edge electrode,elongated in a direction perpendicular to the direction of How, on oneside of the gaseous ow and a second electrode, elongated in a directionperpendicular to the direction of flow, on the other side of the gaseousow; means, including said knife-edge electrode and said second elongatedelectrode means, for providing a corona discharge into the flow withinsaid nozzle; a collector electrode spaced from said nozzle; and outputmeans connected to said collector electrode.

2. The device as recited in claim 1 including means for providing asecondary ow of gaseous material of a lower pressure than said highpressure gaseous material past both 5 sides of said nozzle.

3. The device as recited in claim 2 wherein said elongated knife-edgeelectrode and said second electrode are annular electrodes forming anannular divergent nozzle.

4. The device as recited in claim 3 wherein said nozzle surrounds saidcollector electrode and said nozzle provides a radial stream directedinwardly toward said collector electrode.

5. The device as recited in claim 3 wherein an annular shieldingelectrode is positioned between the nozzle and the collector electrode.

6. The device as recited in claim 5 wherein said nozzle surrounds saidcollector electrode and said nozzle provides a radial `stream directedinwardly toward said collector electrode.

7. The device as recited in claim 5 wherein said gaseous material is ahigh pressure vapor.

8. The device as recited in claim 7 wherein said nozzle surrounds saidcollector electrode and said nozzle provides a radial stream directedinwardly toward said collector electrode.

References Cited UNITED STATES PATENTS 2,784,114 3/1957 Miller 117933,212,878 10/1965 Bouteille 75--34 X 3,400,513 9/1968 B011 55--10-33,417,267 12/1968 Marks 310-6 DAVID X. SLINEY, Primary Examiner

